Method of desensitizing lead azide and tetryl



United States Patent 3,265,545 METHOD OF DESENSITIZING LEAD AZIDE AND TETRYL Eugene J. Murray, East Orange, N.J., assignor to the United States of America as represented by the Secreta'ry of the Army No Drawing. Filed Sept. 2, 1964, Ser. No. 394,087 5 Claims. (Cl. 14935) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates generally to new explosives and more particularly concerns improved methods of treating certain explosives to render them less sensitive to detonation by accidental mechanical shock.

Desenitization of solid and liquid explosives is not new. Those liquid explosives, for example, which were considered to be dangerously sensitive to mechanical shock, e.g., nitroglycerin, are ordinarily diluted with a nonexplosive material which is compatible with the liquid explosive. This method of desenitization was subject to one disadvantage which detracted considerably from the usefulness of the desensitized explosive. That is, a rather large amount of desensitizing agent was required to produce an explosive of sufficiently low sensitivity for safe handling and storage. Accordingly, explosives desensitized by this method were characterized by marked reduction in the explosive power. Persons using these liquid explosives were faced with a dilemma which usually could be solved only by the unsatisfactory compromise of employing a minimum amount of desensitizer so that the explosive provided only marginal safety in its handling and use.

Desensitization of solid explosives by parafiin waxes or mineral oils, for example, suffer generally from a non-uniformity of coating of each grain or crystal and causing the crystal to segregate by exudation of the oil or wax. Further, the use of waxes and oils requires specialized equipment and is adversely alfected by unfavorable environmental conditions resulting in poor shelf life and less than 100% reliability.

The present invention overcomes these and other difficulties by providing new explosives comprising tetryl or lead azide which are rendered more insensitive to shock by treatment with suit-able organic dyes, the resultant product being capable of withstanding impact tests and yet having a good shelf life without undergoing deleterious changes in properties.

It is therefore a broad object of this invention to provide an easily manipulatable lead azide or tetryl explosive which can be safely loaded and transported.

Another object of the invention is to provide methods of making these explosives.

Still another object of the invention is to provide a generally insensitive lead azide or tetryl explosive and methods of making therefor, both of which are substantially free of the aforementioned disadvantages.

Other and further objects of the invention will be apparent to those skilled in the art upon study of this disclosure.

, In accordance with my invention, PbN (lead azide) and tetryl (2,4,6-trinitrophenylmethyl nitramine) are rendered less hazardous in their handling and manufacture by suitable treatment with water soluble organic dyes such as 1-methylamino-anthraquinone, rosaniline, Calco Oil Blue NS and Calcophen Red Y, a non-subliming azotype dye.

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The selected dye must be chemically non-reactive with the explosive and soluble in common solvents such as acetone, ethyl alcohol or methyl alcohol. The final product should have no negative charges thereon and thereby minimizing any danger of accidental electrostatic detonation.

Example 1 Ten parts by weight of powdered dye, in this instance 1-methylaminoanthraquinone, is dissolved in about 200 parts by weight acetone in a metallic round-bottom vessel. About 1,000-2,000 parts by weight of alcohol-wet lead azide explosive are mixed with about 1-2 parts by weight polyvinyl pyrrolidone (PVP which is soluble in alcohol or water such that about 0.1% by weight of PVP is incorporated into the explosive. The PVP is used to improve the affinity of the explosive for the dye such that the latter will complex with the PVP to render the final coating water insoluble. The PVP-treated lead azide may now be slowly added to the acetone-dye solution with gentle stirring. The resultant mixture is then heated to 5060 C. with stirring until dry. The coated lead azide will then be placed in a tray and heated again to about 60 C. until complete dryness is assured and then stored in approved containers. The final desensitized product will consist of about 9999.7% by weight lead azide having about 0.34% by weight of dye coating complexed thereon.

The product is stable at C. and is capable of withstanding a ten-inch drop test and a friction sensitivity test without exploding whereas the prior art dextrinated lead azide exploded when subjected to the drop test aforementioned at three inches and was considerably more frictionally sensitive. The drop test comprises permitting -a two kilogram steel cylinder to freely fall into a metal cylinder approximately one and a half inches inside diameter and about four-inches long onto a specified quantity of explosive contained therein. The friction test involves a swinging pendulum which is caused to abrade a specified quantity of explosive.

Example II About ten parts by weight rosaniline,

[ 3 s a zl OOH [C6H4NH2] 2,

is dissolved in about 300 parts by weight acetone in a metallic round-bottom vessel. About 1,500-2,500 parts by weight tetryl is islurried with a sufficient quantity of water and then treated with PVP such that about 0.l- 0.2% by weight PVP remained on the explosive when calculated in the dry state. The PVP-treated tetryl is now slowly added to the acetone-rosaniline solution with gentle stirring. The resultant mixture is then heated to about 60 C. with stirring until dry. The coated tetryl will then be placed in a tray and heated again to about 60 C. until complete dryness is assured and then stored in approved containers. The final desensitized product will consist of about 99-99.7% by weight tetryl having about 0.3%1% by weight of rosaniline coating complexed thereon.

The product is stable at 120 C. and is capable of Withstanding a 14-inch drop test whereas the untreated tetryl successfully withstood only a 6-inch drop test. Further, my desensitized tetryl is frictionally non-sensitive when compared to the untreated tetryl.

Example III Ten parts by weigh-t of powdered dye, in this instance Calco Oil Blue NS, is dissolved in about 200 parts by 3 weight acetone in a metallic round'bot'tom vessel. About LOGO-2,000 parts by weight of alcohol-wet lead azide explosive are mixed with about 12 parts by weight polyvinyl pyrrolidone (PVP). The preparation procedure then proceeds as indicated in Example -I. The Calco Oil Blue NS has the formula The final desensitized tetryl product withstood the drop and friction tests aforedescribed substantially identical with the l-methylamino-anthraquinone coated lead azide.

The invention is not to be construed as limited in any manner by the foregoing illustrative examples but is susceptible of many modifications and alterations without departing from the spirit or scope thereof. Accordingly, the invention is to be defined only by the scope of the appended claims.

I claim:

1. A desensitized explosive consisting essentially of about 99-99] weight percent of a member selected from the group consisting of lead azide and tetryl and about 0.34% of a dye selected from the group consisting of 1-methylamino-anthraquinone, rosaniline, Calco Oil Blue NS, and Calcophen Red Y.

2. An explosive according to claim 1 wherein said member comprises lead azide.

3. An explosive according to claim 1 wherein said member comprises tetryl.

4. A method of desensitizing lead azide comprising the steps of dissolving about one part by weight of an organic dye selected from the group consisting of l-methylaminoanthraquinone, rosaniline, Calcophen Red Y, and

Calco Oil Blue NS in about 200300 parts by weight of acetone to form a solution,

mixing a suificient quantity of PVP with alcohol-wet lead azide such that about 0.l0.2% PVP is incorponated into said lead azide when calculated on a dry ibasis,

slowly adding the PVP-treated lead az-ide to said solution to form a mixture,

drying said mixture until the resultant desensitized explosive contains about 0.3-l% of said dye.

5. A method of desensitizing tetryl comprising the steps dissolving about one part by weight of a dye selected from the group consisting of l-methylamino-anthraquinone, rosaniline, Calco Oil Blue NS and Calcophen Red Y in about 200-300 parts by weight acetone to form a solution,

slurrying said tetryl by mixing with water,

mixing a sufiicient quantity of PVP into said slurrying tetryl such that the resultant mixture contains about 0.10.'2% PVP when said tetryl is calculated on a a dry basis,

slowly adding the PVP-treated tetryl to said solution to form a mixture, and

drying said mixture until the resultant desensitized tetryl contains about 0.3-l% of said dye.

No references cited.'

BENJAMIN R. PADGETT, Acting Primary Examiner.

S. J. LECI-lERT, Assistant Examiner. 

1. A DESENSITIZED EXPLOSIVE CONSISTING ESSENTIALLY OF ABOUT 99-99.7 WEIGHT PERCENT OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF LEAD AZIDE AN TETRYL AND ABOUT 0.3-1% OF A DYE SELECTED FROM THE GROUP CONSISTING OF 1-METHYLAMINO-ANTHRAQUINONE, ROSANILINE, CALCO OIL BLUE NS, AND CALCOPHEN RED Y. 